Improvement of reliability and robustness of semiconductor devices is an ongoing aim in the development of semiconductor device and particularly power semiconductor devices. To ensure that devices which were delivered to customer meet the demands, the semiconductor devices are subjected to extended reliability tests before delivery. For example, the properties of the semiconductor device during an avalanche breakdown influence the reliability and are therefore subject for further developments. Transient avalanche breakdowns frequently occur in demanding applications and can render a device useless.
Two main device concepts having different avalanche properties are commonly used—the field electrode concept and the dense trench concept. In semiconductor devices of the field electrode concept, the avalanche breakdown occurs close to the contact plug for contacting the body region. Different thereto, the location of the breakdown is arranged close to the bottoms of the trenches in semiconductor devices formed according to the dense trench concept. While semiconductor devices of the trench dense concept exhibit improved properties regarding on-state resistance in comparison with standard devices of the field electrode concept, dense trench devices are more susceptible to avalanche breakdowns.